Heat dissipation in devices that have an internal energy supply

ABSTRACT

The invention relates to heat dissipation with devices with an internal energy supply device. A housing device for an electrical load and an energy supply device are provided, especially a laptop housing, having a device for heat dissipation in order to transport the heat generated by the energy supply device by means of at least one flowing medium to at least one outer surface of the housing device and to discharge it via the outer surface.

FIELD OF THE INVENTION

The invention relates to the heat dissipation of electrical deviceswhich are operated with an internal energy supply, in particular with afuel cell device. A main field of use for the invention is portablecomputers.

STATE OF THE ART

Generally, small electrical devices are supplied with current fromnon-rechargeable or rechargeable batteries located in the housing. Theobjective in the initial and on-going development of mobile electricaldevices has two main features: the maximum possible performance in adevice which is as compact as possible. The requirement for compactnessgives rise to ever smaller outer dimensions and/or a flat constructionwith correspondingly small outer surfaces, by means of which the heatgenerated by the loads in the interior of the housing must bedissipated. The cooling of the energy supply device has received littleattention until now, because with non-rechargeable and rechargeablebatteries, this does not play a significant role due to the low amountof inherent heat generated.

Even though a network-independent energy supply withnon-rechargeable/rechargeable batteries is currently the normal case,with increasingly high performance consumer loads, increasingly highperformance energy supply devices must be made available which are moresuitable for long-term operation. With the rapid rate of development offuel cells recently, a more significant emerging trend is therealisation of the energy supply of these types of electrical devicesusing fuel cells instead of non-rechargeable/rechargeable batteries.

With the use of fuel cells for small electronic devices the heatgenerated by the internal energy source is however not negligiblecompared to the heat generated by the loads. Consequently, the problemof heat dissipation (“cooling”) becomes more pronounced.

It should be pointed out at this point that in this application theterms “heat dissipation” and “cooling” are used synonymously inaccordance with the usual language used in the technology. A primeexample of the problem outlined above are portable computers (notebooks,laptops, PDAs, organisers, etc.), which, for the sake of simplicity andwithout restricting generality, are referred to as laptops. Therefore,the invention is explained essentially with reference to the field ofuse of the portable computer for which it is particularly predestined.However, it should be understood that the invention is not restrictedsolely to this field. In particular, mobile telephones of primarily thenew generation of internet-compatible mobile telephones and alsoportable equipment with monitors (portable televisions, measurementdevices, medical equipment for the emergency services, etc.) are fieldsof use for the invention.

The core of the computer is the electronics and in particular theprocessor, for which adequate cooling is an absolute necessity and whichaccordingly exhibits a high state of development. That which makes theportable computer a particularly suitable field of use is its flatconstruction. In comparison to its volume, the portable computer has alarge surface, which in the operating state is almost doubled due to thefold-out swivelling screen.

FIG. 1 is a schematic view of a conventional portable computer withhinged screen section. The four outer surfaces of the laptop whichdominate from a size point of view are numbered from 1 to 4: 1designates the bottom surface of the base plate of the laptop, 2 theupper side of the base plate of the laptop, mainly taken up by thekeyboard, and 3 and 4 are the front and back of the hinged screen lidrespectively.

For various reasons, with the laptops currently available on the marketnone of these four surfaces play a significant role in heat dissipation.The bottom surface 1 is only conditionally suitable, because the heatdissipation requires air circulation with the ambient air. The surface 2on the keyboard side is largely taken up by the keyboard and otheroperating controls, whereby the keys and other operating surfaces arenot well suited to heat dissipation due to construction and/oroperational reasons. The hinged screen lid would be particularlysuitable for heat dissipation, in particular the back 4. However, inthis case the heat needs to be transported from the housing partexhibiting the processor to the screen lid, which can only be ensured inan adequate manner by a flowing medium. Although consideration is takingplace in this direction, cf. for example U.S. Pat. No. 5,383,340 andU.S. Pat. No. 5,634,531, these concepts have not become established dueto the substantial technical complexity. An alternative is the provisionof the active electronic loads in the screen lid, which has also beensuggested in U.S. Pat. No. 5,383,340 and in the U.S. Pat. No. 6,181,555and U.S. Pat. No. 5,982,617. Therefore generally, processors are onlycooled by a fan through a ventilation hole L in the small rear outersurface of the laptop housing.

Therefore one object of the invention is the effective dissipation ofheat generated by the operation of the energy supply device inelectrical devices with an internal energy supply device.

In particular an object of the invention is to improve the possible usesof fuel cells for the energy supply of electronic devices.

DESCRIPTION OF THE INVENTION

The objects described above are solved according to the invention by thehousing device with the features of Claim 1.

Accordingly, the housing device, which provides accommodation for anelectric load and its energy supply device, comprises a device for heatdissipation in order to transport the heat generated by the energysupply device by means of at least one flowing medium to at least oneouter surface of the housing device and to discharge it via the outersurface.

For the dissipation of heat from the energy supply device to the outersurface, heat transport by means of a flowing medium is substantiallymore efficient than (electronic and/or phononic) thermal conduction orthermal radiation. Both of the latter processes can though provide asupporting contribution, in particular with the uniform distributionover the outer surface (thermal conduction) and with the discharge tothe ambient surroundings (thermal radiation).

Since “housing” is usually taken to signify a rigid outer envelope witha specific and non-varying outer shape, here the general expression“housing device” is used, which is intended to indicate that theinvention can be used not only for simply formed housings, but also forhousing devices of many housing parts connected together and optionallymovable relative to one another. Particularly, it is with such housingdevices that the concept according to the invention can be realisedespecially advantageously.

Whereas in conventional housing devices with an integral energy supplydevice, no particular consideration is given to the heat dissipationfrom the energy supply device and this at best occurs by means of thenatural convection of the air in the housing device and thermalconduction through the housing parts, the invention provides for anactive device for heat dissipation, which facilitates the use of energysupply devices with comparatively substantial generation of heat. Theflowing medium (or one of the flowing media) can be the air available inthe housing device. With fuel cells as the energy supply devices theflowing media can comprise their waste gases. In these cases the heatdissipating active device comprises, for example, one or more blowerswith which far more effective air flows or gas flows can be created forheat dissipation than in comparison to natural convection. However,media provided specially for heat dissipation can also be used, forexample in a cooling circuit or heat pipe.

Therefore, the device for heat dissipation in a particularly preferredfurther development of the invention comprises a pipe system for atleast one flowing fluid providing thermal transport and integrated intothe housing device.

This pipe system can be integrated into the wall of the outer surface(s)at least in the region of the outer surface(s) that are effectivelythermally active, which has the constructional advantages in that thethermal transfer to the outer surface is improved and a more efficientexploitation of the interior space is facilitated.

In the region of the outer surface the pipe system can exhibit adistribution and/or meander structure in order to integrate a surfaceproportion as large as possible into the thermal discharge in order toincrease the efficiency.

In an advantageous further development hinged and/or extractable devicesare provided on or in the housing device, with the aid of which thesurface of the housing device that can be used for the thermal dischargecan be enlarged.

This further development is primarily practicable when the “intrinsic”outer surfaces are not suitable for thermal discharge or their area isnot sufficient, i.e. in particular with compact devices with small outersurfaces.

Similarly, to increase the effectiveness of the thermal discharge it maybe appropriate to provide the outer surfaces used for thermal dischargewith surface-enlarging structural features: the surface enlargement canbe achieved macroscopically by means of protruding elements such ascooling fins or by a corrugated surface, but also microscopically bymeans of an increased surface roughness and/or by a porous surfacestructure.

It is only pointed out and no detailed explanations are necessary to saythat for increasing the effectiveness of heat dissipation thecontribution due to heat radiation must under some circumstances also betaken into account. It may therefore be quite practicable to apply acoat of paint to the outer surfaces to improve the radiation emission.

Alternatively or in addition to this, the device for heat dissipationcan comprise at least one fan (blower), in order to improve the aircirculation—and therefore the heat transfer to the ambientsurroundings—on at least one of the outer surfaces used for thermaldischarge.

The concept according to the invention can be used with any electricaldevice with integral energy supply. It is however particularlypracticable if this energy supply device is a fuel cell device orcomprises one, because the heat generated by a fuel cell device isnormally significantly higher than with comparable energy supply devicessuch as primary and secondary cells.

In an advantageous further development the device for heat dissipationis formed such that it is also suitable for dissipating the heatgenerated by the electrical load. This means for example that the pipesystem for the flowing fluid can be routed past the electrical load andtake up and dissipate the heat generated by the electrical load by meansof suitable heat exchanging devices.

A particularly preferred field of use for the invention is the portablecomputer whose housing device can be retrofitted according to thefeatures described above or—as is normally to be preferred—can bedesigned from the start according to these details. Apart fromconventional portable computers, more or less significant variations inthe arrangement of the housing parts can be preferred, some of which arequoted as preferred embodiments in the following description of thefigures.

In particular with conventional portable computers, the back of the flatscreen is especially suitable as an outer surface for heat dissipation,because it is comparatively large and also does not have any furtherfunctional task. Under some circumstances however the front of thescreen can also be used for heat dissipation.

With a particularly preferred further development, which in particularsimplifies the formation of the pipe system, the energy supply device isaccommodated in the housing section which includes the screen. In thiscase the fluid does not need to be routed via various (swivelling)housing parts which move relative to one another.

Preferably, the device for heat dissipation is formed such that inaddition to the cooling of the energy supply device, effectivedissipation of the heat generated by the computer electronics (inparticular the processor unit) is also achieved.

This means for example that in the case of a DMFC a fuel cell can beused as an energy supply device with discharge air at a temperature of60° C. to cool the processor having a somewhat higher temperature.

The basic principles of the invention are explained in the followingwith reference to the enclosed figures based on a particularly suitablefield of use for the invention, i.e. a portable computer powered by fuelcells.

The following are shown:

FIG. 1 a schematic view of a conventional portable computer;

FIG. 2 a schematic view of a first preferred embodiment of thisinvention;

FIGS. 3-5 schematic detail views for the practical implementation of theconcepts on which the invention is based;

FIG. 6 a schematic view of a second preferred embodiment of thisinvention;

FIG. 7 a schematic view of a third preferred embodiment of thisinvention;

FIG. 8 a schematic view of a fourth preferred embodiment of thisinvention;

FIG. 9 a schematic view of a fifth preferred embodiment of thisinvention;

FIG. 10 a schematic view of a sixth preferred embodiment of thisinvention.

With regard to FIG. 1 the introduction to the description has alreadymentioned it. It shows a schematic view of a hinged portable computerwith a housing section T lying on the table surface and a diagonallystanding screen lid B. The figure is only used to show the structuralconditions forming the basis on which the use of the invention onportable computers is based. Apart from the keyboard on the upper side2, the housing section T generally contains all the essential componentsof the computer electronics and the energy supply device required forthe electronics.

With a laptop powered by conventional rechargeable batteries the fourlarge outer surfaces 1-4 of the hinged housing contribute to the heatdissipation of the heat generated during laptop operation, but thisamount is not sufficient. Therefore, the processor is usually cooled bymeans of a fan via an air hole L in the back of the housing section T.

FIG. 2 shows a schematic view of a first preferred embodiment of thisinvention. In contrast to the laptop in FIG. 1, the laptop sketched inFIG. 2 is powered by a fuel cell device accommodated in the housingsection T. In order to be able to dissipate the heat generated by thefuel cell device from the housing section T to a sufficient extent, thelarge surface of the free standing lid unit B is used.

In this respect the heat generated in the housing section T must betransported to the screen lid B. Preferably, the transport occurs bymeans of a flow medium which takes up the heat generated by the energysupply device in the housing section T, passes it from the housingsection T by means of flow devices, of which only the schematicallysketched flexible hose 6 is drawn in the figure, to the lid B anddischarges it to the ambient surroundings.

Especially for the case where the energy supply device comprises a fuelcell device, the fluids used for the heat dissipation can comprisefluids used in the operation of the fuel cell device and/or reactionproducts occurring with it.

Two appropriate embodiments are sketched in FIGS. 3A-3C and 4A-4C(different views in each case).

First regarding FIG. 3: As indicated in FIG. 3A, heated (gaseous orliquid) fluid flows from the fuel cell 10 provided in the housingsection T through the pipe 6 to the lid unit B, where it is distributedin the cover unit by means of a distribution structure 9, such that asurface as large as possible can be used for thermal discharge to theambient surroundings, as indicated in FIG. 3B. Here, the heatdissipation can optionally occur—depending on the type and physicalcondition of the fluid—in that the fluid itself is discharged to theambient surroundings, which for example in the cases of air, carbondioxide and water vapour presents relatively little problem. In thiscase the area provided for the discharge, which is sketched in the planin FIG. 3C, preferably exhibits a porous structure.

Also particularly suitable for heat dissipation is though a circulatoryflow between the source of heat (fuel cell 10) and the heatsink (lidunit B), which is schematically indicated in FIG. 4A. This version isprimarily preferable when, during the operation of the fuel cell, fluidsare used which can be fed on the input side as well as (under somecircumstances in a changed composition) occur on the output side.Examples of these types of fluids are water and air. For the efficientexploitation of the outer surface of the lid unit B a distributorstructure 9 is provided in or immediately below the outer wall, forexample in the form of a meander flow guide (cf. FIG. 4A, 4B). Toimprove the heat exchange with the ambient surroundings,surface-enlarging structures can be provided: for example the outersurface can exhibit a corrugated structure and/or be provided with fins(indicated in FIG. 4 c).

The closed cooling circuit can also be independent of the energy supplydevice, which has the advantage that the fluids or fluid mixtures mostsuitable in the relevant temperature range can be used for heatdissipation. This type of arrangement is illustrated schematically inFIG. 5. Here, the heat dissipation occurs by means of a separateenclosed circuit, provided specifically, whereby the fluid flowing inthis circuit takes up the heat generated by the energy supply device 10by means of a heat exchanger 11—in the case of a fuel cell device forexample in a counter-flow process with the heated fluids of the fuelcell device.

The type of heat dissipation described in FIGS. 4 and 5 can, withsuitable fluids or fluid mixtures, be formed as a two-phase circuit, inwhich the liquid medium evaporates on taking up heat, flows in thegaseous state from the fuel cell 10 to the distributor structure 9,condenses there on discharging heat and is then fed back again incondensed form to the fuel cell 10.

With the description of the sketched examples it has been assumed thatthe natural convection occurring on the surface is sufficient for heatdischarge to the ambient surroundings. However, if required, fans can beprovided to reinforce the convection. If the housing section Bexhibiting the screen is used for cooling (as described for example inconjunction with FIG. 2), then the screen side 3 can be thermallyinsulated from the back 4 acting as the cooling surface. If this is notnecessary, or if—with low outdoor temperatures—heating of the screen isadvantageous, then also the screen side 3 of the lid unit B cancontribute to the heat dissipation.

FIG. 6 is a schematic view of a second preferred embodiment of theinvention. In contrast (alternatively also additionally) to theembodiment shown in FIG. 2, here a separate cooling surface 7 isprovided, which can be swivelled out from the lid unit B and provided onboth sides with fins to reinforce the cooling effect. In the exampleillustrated this cooling surface 7 can be supported by the underlyingsurface, so contributing to the support of the lid unit B. The lattermay primarily be desirable when the fuel cell device is integrated intothe lid unit B.

Alternatively or in addition to the embodiments sketched in FIGS. 6 and8-11, separate cooling surfaces can be provided which can be swivelledout to the side or to the front, as schematically indicated in FIG. 7.On discharging the heat, these cooling surfaces can be used for heatingthe ambient air in the front region of the screen surface, whichimproves the possible uses at low outdoor temperatures. At the same timethese surfaces can be used as viewing shades, as guards againstinterfering light incident at the side and as protection of the screenagainst other ambient effects (e.g. rain drops, splashed water).

An effect of the cooling surface 7 supporting the screen B is primarilypracticable when—as is illustrated by the embodiment of FIG. 8—both theenergy supply device (for example a fuel cell device) and also theessential electronic components are integrated into the housing sectionB exhibiting the screen. In this case the unit T lying flat on theunderlying surface need only exhibit the devices required for manualoperation, in particular the keyboard and can therefore be constructedto be very flat, for example as a so-called touchpad.

FIG. 9 shows an embodiment based on similar principles as in FIG. 7, inwhich the electronics and the energy supply are integrated in onehousing main section H. The screen and keyboard sections B and T can beswivelled out from this housing main section H and can be formed as thinlayers or pads. The main housing H, which exhibits both the fuel celldevice and the electronics, in this case stands diagonally and canalternatively contribute with one or both large housing surfaces to theheat dissipation. In the example in the sketch both large housingsurfaces are provided with fins 5 for heat dissipation. The advantage ofthis embodiment is that the fluid does not need to be routed viaswivelling axes.

FIG. 10 shows an alternative embodiment which also implements theprinciples of the embodiment of FIG. 7. The common swivelling screenunit B and keyboard unit T are fitted to one side of an upright standingmain housing H, whereas on the other side the cooling surface 7 isfitted which also swivels and provides a supporting function.

This invention is particularly well-suited to those devices havingswivelling large-area housing sections. The objective of the inventionis to dissipate the heat generated by the internal energy supply deviceof an electrical device in an efficient manner. It should also beunderstood however that in addition to this, the heat generated byinternal loads (processors, motors, etc.) can also be dissipated. Thefield of use can be extended to devices without large-area housing outersurfaces if they are equipped with swivelling and/or extractablesurfaces or other devices (e.g. cooling coils) for the purposes ofthermal dissipation.

1. Housing device for an electrical load and an energy supply device,comprising: a device for heat dissipation to transport the heatgenerated by the energy supply device by means of at least one flowingmedium to at least one outer surface of the housing device and todischarge it via the outer surface.
 2. Housing device according to claim1, in which the device for the heat dissipation comprises a pipe systemintegrated into the housing device for at least one flowing fluidproviding the heat transport.
 3. Housing device according to claim 1,with swivelling and/or extractable devices to enlarge the outer surfaceof the housing device usable for the heat dissipation.
 4. Housing deviceaccording to claim 1, in which at least one of the outer surfaces usedfor the heat dissipation exhibits surface-enlarging structural featuresto improve the heat dissipation.
 5. Housing device according to claim 4,in which the surface-enlarging structural features comprise an increasedsurface roughness and/or cooling fins and/or surface corrugation and/ora porous surface material.
 6. Housing device according to one claim 1,in which the device for heat dissipation comprises at least one fan toimprove the air circulation on at least one of the outer surfaces usedfor heat dissipation.
 7. Housing device according to claim 1, in whichthe energy supply device comprises a fuel cell device.
 8. Housing deviceaccording to claim 1, in which the device for heat dissipation is formedsuch that the heat generated by the electrical load can also bedissipated.
 9. Portable computer with a housing device according toclaim
 1. 10. Portable computer according to claim 9, in which the outersurface used for heat dissipation comprises the front and/or back of aflat screen.
 11. Portable computer according to claim 9, in which theenergy supply device is provided in the housing section comprising thescreen.
 12. Portable computer according to claim 9, in which the devicefor heat dissipation is formed such that the heat generated by theelectrical load can also be dissipated, and in which the device for heatdissipation is formed such that the heat generated by the computerelectronics can also be dissipated.
 13. Portable computer according toclaim 10, in which the energy supply device is provided in the housingsection comprising the screen.
 14. Portable computer according to claim10, in which the device for heat dissipation is formed such that theheat generated by the electrical load can also be dissipated, and inwhich the device for heat dissipation is formed such that the heatgenerated by the computer electronics can also be dissipated. 15.Portable computer according to claim 11, in which the device for heatdissipation is formed such that the heat generated by the electricalload can also be dissipated, and in which the device for heatdissipation is formed such that the heat generated by the computerelectronics can also be dissipated.
 16. Housing device according toclaim 2, with swivelling and/or extractable devices to enlarge the outersurface of the housing device usable for the heat dissipation. 17.Housing device according to claim 2, in which at least one of the outersurfaces used for the heat dissipation exhibits surface-enlargingstructural features to improve the heat dissipation.
 18. Housing deviceaccording to claim 3, in which at least one of the outer surfaces usedfor the heat dissipation exhibits surface-enlarging structural featuresto improve the heat dissipation.
 19. Housing device according to claim2, in which the energy supply device comprises a fuel cell device. 20.Housing device according to claim 3, in which the energy supply devicecomprises a fuel cell device.